Transparent solder mask led assembly

ABSTRACT

A substrate for an LED assembly can have a plurality of cups formed therein. At least one cup can be formed within another cup. The cups can be co-axial with respect to one another, for example. A machined surface of the substrate can enhance reflectivity of the LED assembly. A transparent and/or non-global solder mask can enhance reflectivity of the LED assembly. A transparent ring can enhance reflectivity of the LED assembly. By enhancing reflectivity of the LED assembly, the brightness of the LED assembly can be increased. Brighter LED assemblies can be used in applications such as flashlights, displays, and general illumination.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is related to U.S. patent application Ser. Nos.[Docket No. M-17453], [Docket No. M-17454], [Docket No. M-17455],[Docket No. M-17459] all filed on the same date herewith, the entirecontents of all of which are expressly incorporated herein by reference.

TECHNICAL FIELD

The present invention relates generally to light emitting diodes (LEDs).The present invention relates more particularly, for example, to methodsand systems for packaging LEDs.

BACKGROUND

Light emitting diodes (LEDs) are well known. LEDs are commonly used asindicators on electronic devices. For example, the red or green powerindicator on many consumer electronic devices, such as CD and DVDplayers, is often an LED.

There is a desire to use LEDs in applications such as flashlights,displays, and general illumination. Brighter LEDs are generally requiredin such applications. However, brighter LEDs require more current andmore current results in the production of more heat. Heat reduces theefficiency of LEDs. Further, some of the light from an LED is oftenwasted, e.g., absorbed, by structures of the LED and/or packagetherefor.

Thus, although contemporary LEDs have proven generally suitable for somepurposes, they possess inherent deficiencies which detract from theiroverall effectiveness and desirability. Therefore, it is desirable toprovide LEDs that can more efficiently use higher current, such as bybetter managing the heat produced thereby. It is also desirable toprovide LEDs that tend to minimize undesirable absorption of lighttherefrom.

BRIEF SUMMARY

Methods and systems for providing brighter LEDs are disclosed herein.For example, an LED assembly having enhanced reflectivity can waste lesslight, such as due to absorption of the light by parts of the LEDassembly.

According to an example of an embodiment, a substrate assembly for anLED assembly can comprise a substrate and a plurality of cups formed inthe substrate. At least one cup can be formed within another cup.

According to an example of an embodiment, an LED assembly can comprise asubstrate and a plurality of cups formed in the substrate. At least onecup can be formed within another cup. At least one LED die can bedisposed within at least one cup.

According to an example of an embodiment, a method for fabricating anLED assembly can comprise machining a first cup in a substrate andmachining a second cup within the first cup. Any desired number of cupscan be machined one inside of another.

According to an example of an embodiment, an LED assembly can comprise atransparent solder mask. The transparent solder mask can enhancereflectivity of the substrate (or of material formed upon thesubstrate).

According to an example of an embodiment, a method for fabricating anLED assembly can comprise forming a transparent solder mask upon asubstrate.

According to an example of an embodiment, an LED assembly can comprise anon-global solder mask. For example, the LED assembly can comprise oneor more local solder masks.

According to an example of an embodiment, a method for fabricating anLED assembly can comprise forming a non-global solder mask upon asubstrate.

According to an example of an embodiment, an LED assembly can comprise asubstrate having a machined surface upon which at least one LED die canbe attached. The machined surface can be deep enough to define a cup orcan be too shallow to define a cup. The machined surface can be deepenough to define a shallow cup. In any instance, the machined surfacecan be more reflective than a non-machined surface.

According to an example of an embodiment, a method for fabricating anLED assembly can comprise machining a surface of a substrate.

According to an example of an embodiment, an LED assembly can comprise atransparent ring.

According to an example of an embodiment, a method for fabricating anLED assembly can comprise attaching a transparent ring to a substrate.

Thus, brighter LEDs can be provided that are suitable for use in suchapplications as flashlight, displays, and general illumination.

Embodiments of the present invention will be more fully understood inconjunction with the following detailed description taken together withthe following drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a semi-schematic, cross-sectional, side view of a lightemitting diode (LED) assembly comprising a plurality of cups (two cups),according to an example of an embodiment;

FIG. 2 is a semi-schematic, top view of an LED assembly, such as that ofFIG. 1, according to an example of an embodiment;

FIG. 3 is a semi-schematic, cross-sectional, side view of a substratehaving a first cup formed therein and having a dielectric formedthereon, as can be used in the fabrication of an LED assembly such asthe LED assembly of FIGS. 1 and 2, according to an example of anembodiment;

FIG. 4 is a semi-schematic, top view of a substrate, such as that ofFIG. 3, additionally having a mask formed upon the top surface thereof,according to an example of an embodiment;

FIG. 5 is a semi-schematic, cross-sectional, side view of a substrate,such as that of FIG. 4, additionally having an adhesion layer, a seedlayer, and a copper layer formed thereon and having the mask removedtherefrom, according to an example of an embodiment;

FIG. 6 is a semi-schematic, cross-sectional, side view of a substrate,such as that of FIG. 5, additionally having a transparent solder maskformed upon a top surface thereof, according to an example of anembodiment;

FIG. 7 is a semi-schematic, cross-sectional, side view of a substrate,such as that of FIG. 6, additionally having a second cup formed therein,according to an example of an embodiment;

FIG. 8 is a semi-schematic, top view of a substrate, such as that ofFIG. 7, showing the solder mask and the conductive layer formed upon thetop surface thereof, according to an example of an embodiment;

FIG. 9 is a semi-schematic, perspective view of another configuration ofa substrate for use in an LED assembly wherein a non-square substrate isused, according to an example of an embodiment;

FIG. 10 is a semi-schematic, top view of another configuration of asubstrate for use in an LED assembly wherein a local solder mask (asopposed to the global solder mask of FIG. 8) is used, according to anexample of an embodiment;

FIG. 11 is a semi-schematic, cross-sectional, side view of a substrate,such as that of FIGS. 7 and 8, additionally having a plurality of LEDdie disposed in the second cup thereof and having a phosphor layerformed over the LED die, according to an example of an embodiment;

FIG. 12 is a semi-schematic, cross-sectional, side view of a substrate,such as that of FIGS. 7 and 8, additionally having a plurality of LEDdie disposed in the second cup thereof and having a clear silicone layerand a phosphor layer formed over the LED die, according to an example ofan embodiment;

FIG. 13 is a semi-schematic, cross-sectional, side view of a substratehaving three cups, having a plurality of LED die disposed in the thirdcup thereof, having a clear silicone layer formed over the LED die, andhaving a phosphor layer formed silicone layer, according to an exampleof an embodiment;

FIG. 14 is a semi-schematic, cross-sectional, side view of a substratehaving three cups, a plurality of LED die disposed in the third cupthereof, having a clear silicone layer formed over the LED die, andhaving a phosphor layer formed silicone layer, wherein individual lensesare formed in the silicone layer and the phosphor layer, according to anexample of an embodiment;

FIG. 15 is a semi-schematic, cross-sectional, side view of a substratehaving a single shallow cup or machined surface formed thereon andhaving a transparent ring surrounding a plurality of LED die disposedupon the machined surface, according to an example of an embodiment;

FIG. 16 is a semi-schematic, top view of a substrate having atransparent ring surrounding a plurality of LED die disposed upon themachined surface thereof, such as that of FIG. 15, according to anexample of an embodiment;

FIG. 17 is a flow chart showing a method for fabricating an LEDassembly, such as that of FIGS. 1 and 2, according to an example of anembodiment; and

FIG. 18 is a flow chart showing a method for fabricating an LEDassembly, such as that of FIGS. 15 and 16, according to an example of anembodiment.

Embodiments of the present invention and their advantages are bestunderstood by referring to the detailed description that follows. Itshould be appreciated that like reference numerals are used to identifylike elements illustrated in one or more of the figures.

DETAILED DESCRIPTION

As examples, methods and systems for packaging light emitting diodes(LEDs) are disclosed. Such methods and systems can provide LEDassemblies that are brighter than contemporary LED assemblies. Forexample, cups having a shiny, machined surface (such as a surface ofbare aluminum) can provide optical reflectivity compared to that ofsilver-plated surfaces, which may be tarnished easily. The use of cupscan further facilitate a robust phosphor/silicone dispensing processthat provides for increased LED light output and better color quality.Such methods and systems can provide LED assemblies with enhanced heatdissipation, such that more current can be used therewith.

As a further example, such methods and system can provide LED assemblieswith mitigated light loss. As those skilled in the art will appreciate,the use of more current in an LED assembly and/or the reduction of lightloss in an LED assembly can result in increased brightness thereof.

According to an example of an embodiment, a substrate assembly for anLED assembly can comprise a substrate and a plurality of cups formed inthe substrate. At least one cup can be formed within another cup. Thesubstrate can comprise a material that has a shiny or reflective surfacewhen machined. The substrate can comprise a material that has good heatconduction. Thus, the substrate can comprise a metal. Non-metalsubstrates can also be used. The substrate can comprise aluminum,copper, aluminum nitride (AlN), ceramic, and/or FR4, for example.

The cups (as well as other surfaces of the substrate) can be formed soas to be substantially reflective. In this manner, light from LEDdie/dice that is incident upon a surface of the cup can be reflectedtherefrom and can contribute to the brightness of the LED assembly.Forming the cups by machining, such as milling, tends to assure that theresulting surfaces are smooth and reflective.

However, other methods for forming the cups can also be suitable. Forexample, the cups can be formed by laser drilling or chemical etching.The cups can then be machined, polished, coated, or otherwise processedto provide a reflective surface thereof.

The cups can be generally co-axial with respect to one another. Anydesired number of cups can be formed at any desired location withinother cups. For example, two cups, three cups, four cups, or more cups,can be formed one within another.

One or more of the cups can be round. One or more of the cups can benon-round, e.g., square. The cups can have any desired shape ofcombination of shapes. For example, the first or outer cup can be roundand the second or inner cup can be square.

The cups can have either sloped or non-sloped walls. Generally, slopedwalls can provide better reflection of light out of a cup. The floorsand/or the walls of the cups can remain bare, e.g., uncoated, so as toenhance the reflectivity thereof. Any coatings applied to the walls canbe transparent or reflective, so as to enhance the reflectivity thereof.

As discussed below, a dielectric layer can be formed upon at least aportion of the substrate. A conductive layer, e.g., a metal layer, canbe formed upon the dielectric layer. A solder mask can be formed uponthe metal layer to facilitate the application of solder thereto. Thesolder mask can be transparent.

The solder mask can be a non-global. For example, the solder mask can bea local solder mask that is formed upon the metal layer substantiallyonly at those locations where a solder mask is required to prevent theapplication of solder. Thus, the solder mask can be formed onlyproximate where the application of solder is desired, such as proximatethe contact pads and/or proximate where the LED die/dice are wire bondedto the metal layer.

The solder mask can be any desired combination of non-global andtransparent. Thus, the solder mask can be both non-global andtransparent.

The use of cups, such as two or more generally co-axial cups, can negatethe need for a ring. As those skilled in the art will appreciate, suchrings are commonly used according to contemporary practice to containlayers of material that are applied over the LED die/dice. For example,such rings can be used to facilitate the application of a clear siliconeand/or a phosphor layer.

One or more cups can contain the layer or layers of material that areapplied over the LED die/dice. For example, the cup or cups can be usedto facilitate the application of any desired number of clear siliconeand/or a phosphor layers. Thus, the use of cups can eliminate the needfor such contemporary rings. However, a ring can be used in combinationwith a cup or machined surface of the substrate, if desired.

According to an example of an embodiment, a method for fabricating anLED assembly can comprise machining a first cup in a substrate andmachining a second cup within the first cup. Thus, the LED assembly cancomprise a plurality of generally co-axial cups, for example.

According to an example of an embodiment, an LED assembly can comprise asubstrate having a machined surface upon which at least one LED die canbe attached. The machined surface can be shiny or reflective such thatlight incident thereon from the LED die/dice. The machine surface candefine a cup or can not define a cup.

One or more cups can be formed in the machined surface. Any surface of acup can be machined. Any desired combination of machined surfaces andcups can be used.

According to an example of an embodiment, a method for fabricating anLED assembly can comprise machining a surface of a substrate. Suchmachining can enhance the reflectivity of the substrate and can thusincrease the brightness of an LED assembly by mitigating undesirablelight absorption.

One or more LED die can be attached to the machined surface. Any desirednumber of LED die/dice can be attached to or proximate a machinedsurface so as to enhance the brightness of an LED assembly. For example,an array of LED die can be attached to the machined surface. The arraycan comprise two LED dice, four LED dice, eight LED dice, or any othernumber of LED dice.

Referring now to FIGS. 1 and 2, a light emitting diode (LED) assemblycan comprise a plurality of cups, according to an example of anembodiment. More particularly, a substrate 101 can have a first cup 102formed therein and can have a second cup 103 formed in the first cup102. The second cup 103 can be formed in the floor of the first cup 102.The first cup 102 can be generally circular in shape (as shown) and thesecond cup 103 can be generally square in shape (as shown). The firstcup 102 and the second cup 103 can be co-axially disposed with respectto one another (as shown).

Alternatively, the first cup 102 can be non-circular and/or the secondcup 103 can be non-square. The first cup 102 and the second cup 103 canbe non-coaxially disposed with respect to one another. For example, thefirst cup 102 and/or the second cup 103 can be oval, triangular, square,rectangular, or octagonal. The first cup 102 and/or the second cup 103can have any desired shape. The first cup 102 and the second cup 103 canhave the same shape or can have a different shape with respect to oneanother. Indeed, the first cup 102 and/or the second cup 103 can haveany desired combination of shapes.

As a further example, the first cup 102 and/or the second cup 103 can beoff center or eccentric with respect to one another (such as when viewedfrom above). The second cup 102 can be disposed at any desired positionwithin the first cup 102. Thus, the second cup 102 can be disposedproximate a wall of the first cup.

Indeed, any desired number of cups may be disposed one within another.Thus, examples of embodiments can comprised one, two, three, four, five,six, seven, eight, or more cups that are disposed one within another.Other examples of embodiments can comprise a single cup.

Indeed, any desired number of cups may be disposed within a given cup.Thus, examples of embodiments can comprised one, two, three, four, five,six, seven, eight, or more cups that are disposed a single cup.

A given cup can have any desired number or configuration of cupsdisposed therein. For example, a given cup can have four cups disposedside-by-side (as opposed to on within another) therein. Thus, atwo-dimensional array of cups can be formed within a cup. The cupswithin a given cup can have the same shape or different shapes.

One or more LED die can be disposed within the second cup 103. Anydesired number of LED die in any desired configuration can be disposedwithin second cup 103. The first cup can have one or more LED diedisposed therein.

Each cup can have the same number or a different number of LED diedisposed therein. For example, two cups can be disposed within anothercup and each of the two cups can have a different number of LED diedisposed therein.

The substrate 101 can comprise a heat conductive material. For example,the substrate 101 can comprise metal. The substrate 101 can comprise asingle metal or any desired combination of metals.

The substrate 101 can comprise a non-metal. Examples of materialssuitable for use as the substrate include aluminum, copper, aluminumnitride (AlN), ceramic, and FR4. As those skilled in the art willappreciate, FR4 is a type of material used for making a printed circuitboards.

A dielectric layer 104 can be formed upon the substrate 101. Forexample, the dielectric layer can cover substantially all of the topsurface of the substrate 101 other than the second cup 103. Typically,the dielectric layer 104 will not be formed upon the walls and floor ofthe second cup 103.

A metal layer 105 can be formed upon the dielectric layer 104. The metallayer 104 can define separate positive and negative conductors thatfacilitate current flow to the LED die according to well knownprinciples. The metal layer 105 can define contact pads 109 thatfacilitate electrical connection between the LED assembly and a powersource.

Wire bonds 108 can interconnect the LED dice 107 with the metal layer105. Wire bonds 108 can interconnect the LED dice 107 in any desiremanner. For example, wire bonds 108 can interconnect the LED dice 107 inany desired combination of parallel and serial.

The bottom of the second cup 103 and the walls of the second cup can bereflective. The first cup 102 and the second cup 103 can be formed bymachining such that the surfaces thereof are smooth and reflective. Forexample, the first cup 102 and the second cup 103 can be drilled,milled, and/or punched into the substrate 101. As those skilled in theart will appreciate, the use of machining provides a smooth surface thatis substantially reflective for light from the LED dice 107.

FIGS. 3 to 16 show methods for forming LED assemblies according toexamples of embodiments. The various features of LED assemblies shown inFIGS. 2 to 16, as well as those shown in FIGS. 1 and 2, can be combinedwith one another, as desired. For example, any desired combination ofcups, machined surfaces, transparent rings, transparent solder masks,and non-global solder masks can be use to fabricate embodiments.

Referring now to FIG. 3, a substrate 101 can have a first cup 102 formedtherein. A dielectric 104 can be formed on the substrate 101. The firstcup 102 can be formed by drilling, as discussed above. The dielectriclayer 104 can be grown globally, e.g., over substantially the entire topsurface of the substrate 101.

The dielectric layer 104 can cover that portion of the substrate 101that does not define the first cup 102 and can cover the floor of thefirst cup 102. The dielectric layer 104 can be omitted from the slopedside 301 of the first cup 102. Alternatively, the dielectric 104 cancover the sloped side 301 of the first cup 102.

The dielectric layer 104 can be formed by anodizing or printing, forexample. The dielectric layer 104 can be formed by any desired method.

Referring now to FIG. 4, a mask 401 can be formed upon the top surfaceof the substrate 101 such that the mask 401 covers a portion of thedielectric layer 401. The mask 401 can also cover a portion of thesubstrate 101 where there is no dielectric layer 104. For example, themask 401 can cover a portion of the sloped sides 301 of the first cup102.

The mask 401 can define an area where the metal layer 105 is notdeposited. The mask 401 can split the top surface of the LED assemblyinto two portions that are isolated from one another. Thus, the mask 401can facilitate the formation of separate positive and negativeconductors as defined by the metal layer 105. The positive and negativeconductors can facilitate electrical connection to the LED dice 107, asdiscussed above.

Referring now to FIG. 5, an adhesion layer and a seed layer can beformed upon the top surface of the substrate 101, such as upon thedielectric layer 104 thereof. The adhesion layer and a seed layer can beformed upon a portion of the sloped side 301 of the first cup 102, whereno dielectric layer 104 is formed.

The adhesion layer and a seed layer can facilitate the formation of acopper layer thereupon. The adhesion layer, the seed layer, and thecopper layer can be formed according to well know principles. The copperlayer can be electroplated upon the seed layer. A layer of silver (Ag),gold (Au) or aluminum (Al) can be deposited upon the copper layer. Thesilver/gold/aluminum layer can define the metal layer 105. The metallayer 105 can comprise any metal or combination of metals.

The mask 401 can be stripped. Stripping the mask can leave thedielectric layer 104 exposed where the mask 401 had previously beenformed. Any desired method can be used for stripping the mask 401.

Referring now to FIG. 6, a transparent solder mask 601 can be formedupon a top surface of the LED assembly, such as upon the metal layer 105thereof. The solder mask can define exposed portions of the top surfaceof the LED assembly where solder is to be applied. The solder can beused to facilitate electrical connections, as discussed herein.

Referring now to FIG. 7, a second cup 103 can be formed in the substrate101. The second cup 103 can be formed generally co-axially with respectto the first cup 102. The second cup 103 can be square in shape (asshown in FIG. 2, for example). The second cup can be formed bymachining. The bare metal surface 701 at the bottom of the second cup103 can remain exposed. This bare metal surface 701 is reflective andprovides a good interface for heat conduction from the LED dies to thesubstrate 101.

Generally, machining provides a smoother, more reflective surface ascompared to etching. Etching can be used to form the first cup 102 andthe second cup 103. If etching is used to form the first cup 102 andsecond cup 103, then additional processing can be used to make theresulting surfaces smoother and more reflective. For example, thesurfaces can be machined, polished, and/or coated after etching to makethe surface smoother and more reflective.

Referring now to FIG. 8, the solder mask 601 and the conductive layer106 can be seen in a top view. The conductive layer 105 can define twoseparate portions that define a positive conductor and a negativeconductor. The positive conductor can comprise an exposed positivecontact pad 801 that is in electrical communication with exposed portion803 of the conductive layer 105 to facilitate electrical connection tothe LED die as discussed herein. Similarly, the positive conductor cancomprise an exposed positive contact pad 802 that is in electricalcommunication with exposed portion 804 of the conductive layer 105 tofacilitate electrical connection to the LED die as discussed herein.

Referring now to FIG. 9, the substrate 901 can have any desired shape orconfiguration. Further, any desired number of positive contact pads 801and negative contact pads 802 can be used. A first cup 102 and a secondcup 103 can be formed generally centrally in the substrate.

Thus, the substrate 901 can have a generally star shaped configuration,as shown in FIG. 9. Such a star shaped configuration can betterfacilitate handling and mounting of the substrate, as compared to thesquare substrate of FIG. 2.

Referring now to FIG. 10, a non-global, e.g., local, solder masks 1001(as opposed to the global solder mask of FIG. 8) can be formed. Suchlocal solder masks 1001 can be applied only in those areas whererequired so as to prevent solder from being applied to the substrate101. In this manner, the amount of solder mask tends to be minimized. Asthose skilled in the art will appreciate, a solder mask can becomeyellowish after long-time LED lighting, thus making the LED colorshifted.

The solder mask can be transparent, so as to mitigate undesirable lightloss. A transparent solder mask can be used either globally ornon-globally. The local solder masks 1001 can be transparent,translucent, or opaque.

Referring now to FIG. 11, a plurality of LED dice 107 can be disposed inthe second cup 103. A phosphor layer 1101 can be formed over the LEDdice 107. As those skilled in the art will appreciate, such a phosphorlayer 1101 can be used to change the color of light emitted by the LEDdice 107.

Use of the first cup 102 and the second cup 103 can facilitate thefabrication of an LED assembly having such a phosphor layer without theuse of a ring. As those skilled in the art will appreciate, contemporaryLED assemblies can use a ring to contain the phosphor layer. As shown inFIG. 11, the phosphor layer 1101 can be contained within the first cup102 and the second cup 103.

As those skilled in the art will further appreciate, elimination of thering simplifies fabrication, improves reliability, and can substantiallyreduce cost. The use of a ring involves not only the added cost of thering itself, but also the cost of purchasing and maintaining the machinethat places the ring upon the substrate. Such rings can be small anddifficult to handle, even for automated processes. Such rings can bow orotherwise deform undesirably during fabrication, making handlingdifficult. The use of such rings decreases yield undesirably.

Referring now to FIG. 12, a clear silicone layer 1201 and a phosphorlayer 1101 can be formed over the LED dice 107. Any desired numberand/or configuration of silicon layers and phosphor layer can be formedover the LED dice 107. Thus, more than one layer of silicon and/or morethan one layer of phosphor can be used.

The use of the first cup 102 and the second cup 103 can eliminate theused of a ring, as discussed above. Thus, a ring is not required tocontain the clear silicone layer 1201 and/or the phosphor layer 1101.

The silicon layer(s) and/or the phosphor layer(s) can be bowed upwardlyas shown in FIGS. 11 and 12. Alternatively, the silicon layer(s) and/orthe phosphor layer(s) can have any other desired shape or configuration.For example, the silicon layer(s) and/or the phosphor layer(s) can begenerally flat as shown in FIG. 13 and discussed below or can beirregularly shaped as shown in FIG. 14 and discussed below.

Referring now to FIG. 13, a generally flat phosphor layer 1101 can beformed upon a generally flat clear silicone layer 1201. Any desiredcombination of surface configurations can be used. For example, onelayer, e.g., the silicone layer, can be substantially flat and the otherlayer, e.g., the phosphor layer, can be non-flat.

Referring now to FIG. 14, the substrate 102 can have three cups formedtherein. Indeed, as discussed herein, the substrate 102 can have anydesired number of cups formed therein. Thus, a third cup 1403 can beformed within a second cup 103 and the second cup 103 can be formedwithin the first cup 102. A plurality of LED die 107 can be disposed inthe third cup 1403.

A clear silicone layer 1201 can be formed over the LED dice 107 and aphosphor layer 1101 can be formed over the silicone layer 1201. Thesilicone layer 1201 and/or the phosphor layer 1101 can have irregularlyshaped surfaces. For example, individual lenses 1402 can be formed inthe silicone layer 1201. Similarly, individual lenses 1401 can be formedin the phosphor layer 1101.

Referring now to FIGS. 15 and 16, a single shallow cup or machinedsurface 1501 can be formed upon the substrate 104. The machined surfacecan provide a desirably clean, reflective, and heat transmissivesurface. Such cleanliness can better facilitate further processing,e.g., the attachment of an LED die 107 thereto. Such reflectivity canfacilitate more efficient, e.g., brighter, LED assemblies. Such heattransmission can facilitate enhance heat flow from the LED dice 107 tothe substrate 101.

A ring 1501 can generally surround the plurality of LED dice 107disposed upon the machined surface 1501. The ring 1501 can besubstantially transparent. The ring can facilitate the use of a clearsilicone layer and/or a phosphor layer (like those of FIGS. 11-14).

Other portions of the substrate 101 can be machined. For example,surface 1503 can be machined. Machining of such other surfaces, e.g.,surface 1503, can provide enhance reflectivity and thus improveefficiency of the LED assembly.

Any desired number of machined surfaces can be formed upon the substrate101. Any desired combination of machined surfaces, cups, and/or ringscan be used.

Referring now to FIG. 17, a method for fabricating an LED assembly cancomprise machining a first cup (such as cup 102 of FIGS. 1 and 2) into asubstrate (such as substrate 101 of FIGS. 1 and 2), as indicated inblock 1701. The first cup can be milled into the substrate.

A dielectric layer can be formed upon the substrate, as indicated inblock 1702. The dielectric layer can be formed generally globally uponthe substrate. The dielectric layer can be omitted from the side walls(such as the sloped side wall 301 of FIG. 3) of the cup. The dielectriclayer can be formed by anodizing, cofiring, laminating, printing, or anyother desired method.

A mask (such as mask 401 of FIG. 4) can be formed upon the substrate, asindicated in block 1703. The mask facilitates the subsequent formationof a metal layer only upon desired portions of the substrate. The maskcan prevent the positive conductor and negative conductor defined by themetal layer from undesirably contacting one another. The mask caninclude at least a portion of the floor or bottom of the cup. The maskcan comprise adhesive tape.

A metal layer can be formed upon the substrate, as indicated in block1704. An adhesion layer, such as of nickel/chromium/titanium (Ni/Cr/Ti),and a seed layer can facilitate formation of the metal layer accordingto well known principles. Copper can be electroplated onto thesubstrate. Following the application of copper, silver and/or gold canbe applied to define the metal layer.

After forming the metal layer, the mask can be removed or stripped, asindicated in block 1705. Then, a solder mask can be formed upon thesubstrate, as indicated in block 1706. The solder mask can facilitatethe application of a solder layer to the substrate. The solder layer canbe used to facilitate electrical connection of the LED die/dice to themetal layer and electrical connection of the metal layer (and thus theLED assembly) to the device in which it is use, e.g., a flashlight orroom light.

A second cup can be formed in the substrate within the first cup, asindicated in block 1707. The second cup can be formed by the same methodas the first cup or can be formed by a different method. The second cupcan have the same shape as the first cup, or can have a different shape(see, for example, the round first cup and the square second cup of FIG.8).

One or more LED die/dice can be attached to the substrate within thesecond cup, as indicated in block 1708. Any desired number of LEDdie/dice can be attached to the substrate. Any desired method forattaching the LED die/dice to the substrate can be used. For example,the LED die/dice can be reflow soldered to the substrate.

The LED die/dice can be wire bonded to the metal layer, as indicated inblock 1709. Any desired method of electrically connecting the LEDdie/dice can be used.

Referring now to FIG. 18, another method for fabricating an LED assemblycan comprise machining a surface (such as machined surface 1501 of FIGS.15 and 16) into a substrate, as indicated in block 1801. For example,the surface can be milled into the substrate.

A dielectric layer can be formed upon the substrate, as indicated inblock 8702. The dielectric layer can be formed generally globally uponthe substrate. The dielectric layer can be formed by anodizing,printing, or any other desired method.

A mask (such as mask 401 of FIG. 4) can be formed upon the substrate, asindicated in block 1803. The mask facilitates the subsequent formationof a metal layer only upon desired portions of the substrate. The maskcan prevent the positive conductor and negative conductor defined by themetal layer from undesirably contacting one another. The mask cancomprise adhesive tape.

A metal layer can be formed upon the substrate, as indicated in block1804. An adhesion layer, such as of nickel/chromium/titanium (Ni/Cr/Ti),and a seed layer can facilitate formation of the metal layer accordingto well known principles. Copper can be electroplated onto thesubstrate. Following the application of copper, silver and/or gold canbe applied to define the metal layer.

After forming the metal layer, the mask can be removed or stripped, asindicated in block 1805. Then, a solder mask can be formed upon thesubstrate, as indicated in block 1806. The solder mask can facilitatethe application of a solder layer to the substrate. The solder layer canbe used to facilitate electrical connection of the LED die/dice to themetal layer and electrical connection of the metal layer (and thus theLED assembly) to the device in which it is use, e.g., a flashlight orroom light.

One or more LED die/dice can be attached to the substrate upon themachined surface, as indicated in block 1807. Any desired number of LEDdie/dice can be attached to the substrate. The machined surfacefacilitates enhanced reflection of light form the LED die/dice so as toenhance the brightness of the LED assembly.

The LED die/dice can be wire bonded to the metal layer, as indicated inblock 1808. Any desired method of electrically connecting the LEDdie/dice can be used.

Thus, one or more rings can be used in combination with one or morecups. For example, a cup can be used to contain a clear silicone layerand a ring can be used to contain a phosphor layer.

In operation, light from the LED die/dice can be better reflected fromthe substrate so as to provide a brighter LED assembly. Moreparticularly, light incident upon the machined cup(s) and/or machinedsurface(s) can be better reflected since machining or other processingof the surface(s) make the surface(s) more reflective. Further, limitingthe amount of solder mask (as in non-global use thereof) and/or using atransparent solder mask desirably enhances the reflectivity of thesubstrate because non-transparent solder masks tend to undesirablyabsorb light from the LED assembly. Further, the use of a transparentring inhibits the undesirable absorption of light thereby.

The use of cups can provide a better heat path from the LED die/dice toa heat sink, package, device, or other heat dissipating structure. Whenone or more cups are formed in a substrate, the thickness of thesubstrate is reduced. Thus, heat from LED die/dice disposed at thebottom of such cup(s) can have a shorter path to a heat dissipatingstructure. Heat can be better managed or dissipated so that more currentcan be used with the LED die/dice, resulting in a brighter LED assembly.

As used herein, the term “cup” can refer to a depression or area oflower elevation, as compared to a surrounding or adjacent area.

As used herein, the term “machined surface” can refer to a surface thathas been worked with a tool so as to be more reflective, as compared toan unworked area. A cup can be a machined surface and vice-versa. Amachined surface can be a depression or area of lower elevation, ascompared to a surrounding or adjacent area, but does not have to be.

As used herein “formed upon” can be defined to include deposited,etched, attached, or otherwise prepared or fabricated upon, such as whenreferring to the forming the various layers.

Similarly, as used herein “on” and “upon” can be defined to includepositioned directly or indirectly on or above. Thus, the metal layer canbe referred to as being formed upon the substrate even though thedielectric layer is disposed therebetween, for example.

As used herein, the term “package” can be defined to include an assemblyof elements that houses one or more LED chips and provides an interfacebetween the LED chip(s) and a power source to the LED chip(s). A packagecan also provide optical elements for the purpose of directing lightgenerated by the LED chip. Examples of optical elements are lens andreflectors.

As used herein, the term “transparent” can be defined to include thecharacterization that no significant obstruction or absorption ofelectromagnetic radiation occurs at the particular wavelength orwavelengths of interest. The term “transparent” can be defined toinclude the characterization that a significant amount of light can passthrough.

One or more embodiments can provide LED assemblies with enhanced heatdissipation, such that more current can be used therewith. One or moreembodiments can provide LED assemblies with mitigated light loss. Asdiscussed above, the use of more current in an LED assembly and/or thereduction of light loss in an LED assembly can result in substantiallyincreased brightness thereof. Such increased brightness can facilitatedused of the LEDs in applications such as flashlights, displays, andgeneral illumination.

Embodiments described above illustrate, but do not limit, the invention.It should also be understood that numerous modifications and variationsare possible in accordance with the principles of the present invention.Accordingly, the scope of the invention is defined only by the followingclaims.

1. An LED assembly comprising a transparent solder mask
 2. The LED assembly as recited in claim 1, wherein the transparent solder mask enhances reflectivity of a portion of the LED assembly.
 3. The LED assembly as recited in claim 1, wherein the transparent solder mask is formed upon a reflective surface.
 4. The LED assembly as recited in claim 1, further comprising a plurality of cups formed in the substrate, wherein at least one cup is formed within another cup and wherein an inner one of the cups is configured to contain at least one LED die.
 5. The LED assembly as recited in claim 1, further comprising a machined surface formed upon the substrate, wherein the machined surface is configured to mount at least one LED die.
 6. The LED assembly as recited in claim 1, wherein the transparent solder mask is non-global.
 7. The LED assembly as recited in claim 1, further comprising ring.
 8. The LED assembly as recited in claim 1, further comprising a transparent ring.
 9. A method for fabricating an LED assembly comprising forming a transparent solder mask upon a substrate.
 10. The method as recited in claim 9, wherein the transparent solder mask is formed non-globally. 